Coating poppet valves



Oct. 17, 1961 D. K. HANINK COATING POPPET VALVES Original Filed Nov. 27, 1953 ATTORNEY United States Patent 3,004,864 COATING POPPET VALVES Dean K. Hanink, Indianapolis, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Original application Nov. 27, 1953, Ser. No. 394,583,

now Patent No. 2,893,349, dated July 7, 1959. Divided and this application Aug. 28, 1958, Ser. No.

5 Claims. (Cl. 117-102) This invention relates to coating poppet valves and more particularly to -an inexpensive apparatus and process for removing excess molten coating metal from such valves.

This application is a division of S.N. 394,583 Hanink, now Patent No. 2,893,349, assigned to the assignee of the present invention.

With the advent of high compression internal combustion engines and the more extensive use of leaded fuels in recent years, the exhaust valves of internal combustion engines have been subject to rapid oxidation and high temperature corrosion by the hot combustion gases. The gases which result from the burning of leaded gasolines are especially detrimental and greatly shorten valve life. Consequently, exhaust valve failure frequently occurs either because of high temperature corrosion of the valve seating face or because of corrosion of the stem immediately beneath the valve head. Severe corrosion of this stem vactually results in its necking down to `a point where the stem will fracture.

To alleviate the aforementioned oxidation and corrosion problem and to provide poppet valves which possess a considerably increased operating life, these valves may be coated with aluminum. A process for coating valves with aluminum is disclosed in my co-pending patent application S.N. 364,673, led lune 29, 1953, now abandoned. This process provides an aluminum coated valve having at or adjacent its surface a thin Ilayer of an alloy of aluminum or aluminum base alloy 4and the base metal of the valve. 'I'his layer is provided at the valve seating face and also may be provided around 'the valve head and neck. IFor best results, the valve should have an extremely thin layer of aluminum or `aluminum base alloy over the lalloy layer.

In order to provide a poppet valve with a uniformly thin layer of coating metal, it is necessary to remove the excess aluminum or other coating metal While still in a molten condition. Moreover, this surplus metal must be removed without damage to the valve or the coating layer.

A principal object of the present invention therefore is to provide a simple, practical, and inexpensive apparatus for controlling the thickness of a metallic coating on a poppet valve.

A further object of the invention is to provide a method of effectively utilizing such an apparatus so as to form a poppet valve having a considerably increased operating life due to a uniformly thin corrosion-resistant layer of aluminum or aluminum base alloy. This process produces a coated valve of high quality in which there is provided a continuous chemical bond at the interface of the coating metal and the base metal.

A simplied flow diagram of the method of vention is as follows:

this inice Immerse valve head in molten salt flux at 280 F. to 1400" F.

Dip valve head in molten aluminum bath at l250 F. to 1325 F.

Rinse valve head-in molten salt flux to remove excess aluminum metal .Air blast seating face for further removal of surplus molten metal Cool the valve head l The above 'and other objects are attained in accordance with the present invention by the use of an apparatus which removes from poppet valves excess molten coating metal which would otherwise drain in an irregular manner if the valves were merely allowed to cool after removal .from the coating bath. This apparatus, which provides the Valves with a generally uniformly thin coating layer, is a simple, yet effective device which removes any surplus molten coating metal by means of -a jet of air or other suitable iluid. Compressed -air is preferably used, the air stream Ibeing directed so as to remove excess aluminum, -for example, in a uniform manner, especially at the seating face, the coated portion of the valve which is most critical. 'Ihe resultant coating layer is extremely thin Xand therefore Will not spall or flake off.

Y Other objects and advantages of this invention will more fully appear lfrom the following detailed description of a preferred embodiment of the invention, reference being made to the accompanying drawing in which:

FIGURE l is a Vertical sectional View, with parts in elevation, of a cylindrical air orifice or air Iblasting lixture especially designed to remove excess molten coating metal from poppet valves immediately after the coating step to thereby provide thinly coated Valves having optimum corrosion resistance properties; and Y FIGURE 2 is a sectional view along the line 2-7-2, of FIGURE 1.

The alloying of the surface portion of the poppet valve with the coating metal, such as aluminum or aluminum base alloy, may be carried out in any desired manner. The preferred method is to apply molten aluminum or aluminum base alloy to the valve under such conditions that the aluminum will form an alloy with the valve material Vand result in the desired layer thinness. Best results are obtained when the aluminum or aluminum base alloy is applied by any of the procedures described in Patent No. 2,569,097, Grange et al., owned by the assignee of .the present invention. An especially advantageous method comprises preheating the valve to a temperature of between approximately 1280 F. and l400 chemical treatment.

F. in a fusedsalt bath consisting essentially of 37% to 57% KCl, 25% to 45% NaCl, 8% to 20% NaSAlFG, and 0.5% Ato 12% All-T3. The valve is thereafter immersed for a short time in la molten bath of aluminum or aluminum basealloy at a temperature of about 1250 F. to 1325 F. Subsequently the valve is removed [from the aluminum bath and rinsed #for a short period of time not in excess of approximately 15 seconds in the fluxing salt. The excess coating material is then removed by means of an air blast in accordance lwit-l1 the present invention. As thus treated, the valve is provided with an extremely thin and uniform coating of aluminum bonded to the base metal by lan intermediate extremely thin and uni-form layer of an alloy of aluminum with the base metal. Y A

A relatively short period of immersion in the aluminum bath is desirable to prevent excessive formation of brittle iron-aluminum alloys. Ordinarily, therefore, the valve being I coated is retained in the molten aluminum or aluminum alloy not more than approximately 10 seconds, a period between and l0 seconds being preferred at present.

The surfaces of the valve to be coated are preferably cleaned prior to the aluminum coating and alloying operation. One satisfactory method is to clean the valves in a molten electrolytic caustic salt (such as the com-V mercially available product called Kolene) at a temperature of about 900 `F. The valves'then may be washed in water and thereafter preferably further cleaned by acid pickling. A suitable acid pickling bath is an aqueous solution containing about 2% hydroiiuoric acid, 7% sulphuric acid andV nitric acid. In some instances the valves may require only a simple degreasing treatment in a chlorinated solvent prior to the aluminum coat ing and alloying operation. Mechanical cleaning methods, such as grit'blasting, sand blasting, hydroblasting, etc., may be employed in some cases to supplement the The steps of degreasing and pickling the valve are not essential to the process, however, as heating in the fused salt prior to immersion'in Vthe aluminum or aluminum alloyl bath will'provide a clean surfaced valve unless it is exceptionally contaminated to begin with.

After the valves have been cleaned, the portions thereof which are' not to be coated may be treated with a suitable stop-olf coating to prevent the aluminum from bonding to or alloying with the base metal at such surfaces. A suitable stop-off material for this purpose is a sodium silicate solution, such as an aqueous solution containing to 50% sodium silicate. If the coating metal is to be applied to the entire head and neck of the valve, the valve stem is normally coated with such a sodiumsilicate solution to withinY 3A to 11A inches of the valve head.

When aluminum or an aluminum base alloy is used as the coating material, the alloy of aluminum should contain about 80% or more of aluminum.` Hence, the word aluminum, when used in the claims to refer to the coating material, isY intended to include not only pure aluminum or commercially pure aluminum, but also aluminum base'alloys containing at least approximately 80% aluminum.

The alloy of aluminum with'the valve material should in all casesl be extremely thin. In general the layer of this alloy should have'a thickness of from 0.0005 inch to 0.0015 inch, the outer aluminum layerhaving a thickness not in excess of 0.004 inch. It is presently preferred that the layerV of the Valloy of aluminum therewith be not over 0.0015'inch inthickness.

Any suitable puppet-valve material may be satisfac-V torily provided with a thin protective coating layer in accordance with the present invention, and this coating maybe applied particularly eifectively'to the typical ferrous-base materialsused to form poppet valves Vof internal, combustion engines. In the case ofv aluminum 4 coated steel valves, the interfacial layer which is formed next to the steel is complex iron-aluminum.

After the valve has been dipped in the fused salt llux and the molten aluminum or aluminum base alloy bath, the formed layer of aluminum or aluminum alloy is thicker or heavier than desired. By passing the coated valve slowly through the molten salt after the aluminum dipping step, some of the excess molten coating metal may Ybe drained oif. However, even after the salt bath rinse, which should not exceed approximately l5 seconds in duration, the molten metal layer is still too thick. Although more of the surplus molten coating metal may be removed by rapidly. vibrating or rotating the coated valve during or after removal from the aluminum or aluminum alloy bath, such procedures frequently result in distortion or improper distribution of the aluminum coating layer on the valve. Hence, an air blast is employed, as will hereinafter be more fully described.

After the air blast, the coated valve is cooled or permitted to cool. The excess flux may be removed as by washing, for example, of the coated valve. Water or other quenching media may be employed to cool the coated valve. Generally, it is preferable to air cool the valve below 800 F. followed by a water quench.

As indicated above, rinsingvof the `valve in the molten salt flux usually serves to drain a substantial portion of the excess aluminum vfrom the valve.k However, the amount of aluminum remaining provides an aluminum overlay between 0.005 inch and 0.01 inch thick. In fact, the resultant irregular coating may be even thicker at localized areas, ranging as thick as 0.025 inch. As hereinbefore explained, such a coating layer is much too heavy to properly protect the base metal of the valve since it tends to crack, check and spall `during valve operation, thereby permitting" erosion of the base metal under the protective coating. Therefore, in order to produce a uniform aluminum coating on the surface and to accurately control the thickness Yof the intermediate iron-aluminum alloy layer, the valves are air blasted to remove excess molten aluminum and provide a smooth surface at the coating locations.

If the procedure hereinafter described is followed in coating ferrous base `poppet valves, the resultant ironaluminum alloy layer ranges from 'approximately 0.0005 inch to 0.0015 inch in thickness, Ywhile the thickness of the aluminum Yoverlay 'does not exceedY about 0.004 inch. It is preferred to have the outer aluminum layer between 0.0005 and 0.0015 inch thick, however, resulting in a combined thickness of the iron-aluminum alloy layer and the aluminum overlay 'of approximately 0.001 to 0.0025 inch. A coating layer of this thickness has demonstrated superior yelding characteristics when the valve seating face is pounded in during service. Small depressions in the seating face of the valvecaused by engine deposits which become lodged between the valve seating face and valve seat Vduring operation remain protected by the surface alloy layer.

Referring more particularly to the drawing, FIGURE l shows a fixture which is especially designed to remove surplus molten aluminum fromfV the head of Va poppet valve, thereby producing a uniform and smooth aluminum coating on the valve surfaces and accurately controlling the thickness of the intermediate iron-aluminum alloy layer. VThe outer Yside walls of this device are formed by a generally cylindrical outer sleeve 10 which preferably has its inner surface internally threaded near its upper end, as indicated at.12. A second generally cylindrical sleeve 14 of smaller diameter than the outer sleeve is coaxially positioned Within the latter and forms the inner side walls ofthe unit.

As shown in FIGURE 2, these two sleeves, each of annular cross-section, are spatially separated radially to form an axially extending airpassage or duct 16 which functions as an air pressure equalizing chamber. A ange 1S extends radially outwardly Vfrom the bottom end of the inner sleeve 14 and has its outer peripheral edge secured to the lower edge of the outer sleeve by silver soldering or other suitable means, as shown at 20. This ange thereby forms an annular lower end wall for the unit and seals the passage 16 at its lower end.

An adjustable insert or head 22 is attached to the upper end of the outer sleeve 10, as best seen from FIGURE 1. 'Ihis adjustable head is shown as comprising a generally cylindrical body or wall portion 24 which is provided at its upper edge with an integral flange 26 extending radially outwardly therefrom. External threads 28 formed on the outer surfaces of the body portion 24 engage the internal threads 12 on the cylindrical outer sleeve '10 to secure the head thereto and to provide it with longitudinal adjustability relative to the sleeve. The lower end surface 39 of the wall of the head 22 is shown as angularly arranged with respect to the axis of the concentric sleeves. Likewise, the upper end 32 of the inner sleeve 14 is provided with a similar obliquely sloping surface which, when the adjustable head is fastened in position, is spatially separated from the end surface 30 of the head, thereby defining an angularly extending orifice 34 therebetween.

In the embodiment of the invention shown in the drawing, this annular oriiice is of a frusto-conical shape and extends from the duct 16 radially inwardly and down wardly to the generally cylindrical central chamber 36 defined by the inner sleeve 14 and the adjustable head 22. A set screw 38, which contacts lthe upper end surface of the outer sleeve 10, may be provided in the upper flange 26. 'Ihis set screw is loosened to permit axial or vertical adjustment of the head 22 so that vthe orice size may be varied and is tightened to hold the head stationary after adjustment.

An air inlet opening 40 is provided in the annular iiange or lower end wall 18 of the unit for admitting air to the passage 16 defined by the head 22, the outer sleeve 10, the side wall of the inner sleeve 14 and the tiange 18. This inlet duct 40 is shown as communicating with an air supply tube or pipe, indicated generally at 42, by means of a pipe nipple 44. One end of this nipple may be attached to the flange 18 by silver soldering, as shown at 46, and the other end threadedly or otherwise suitably connected to the air supply pipe. The upper and lower ends of the central chamber 36 function as air outlets for the device.

A generally centrally located air inlet tube 48, which extends upwardly within the chamber 36, also may be connected to the air supply pipe 42. This tube extends to within a short distance of the head of a puppet valve when the latter is properly positioned within the cha-mber 36. The distance between th-e end of the tube 48 and the valve head should be sufficiently small so that the upward air blast from the tube does not produce excessive turbulence with the downcoming air jet near the valve seating face.

In accordance with the invention, after the poppet valve 50 has been coated with aluminum and, if desired, some of the excess aluminum has been removed in the salt bath, the valve is inserted head downwardly into the passage 12. This is done, of course, before the aluminum has completely solidified, the coating being in a semi-molten or mushy condition. When the poppet valve is in proper position, as shown in the drawing, the valve seating face 52 is in the direct line of travel of air passing through the annular orifice 34. In this manner air which is forced under pressure through the pipe 42 enters the air inlet opening 40, passes through the annular passage 16 and the oriiice 32, and impinges upon the valve seating face, thereby aiding in removing excess molten aluminum which still remains. Due to the angle of the valve seating face, a large proportion of the air is directed over the upper surface of the valve head and along the aluminum-coated neck of the valve stem. Thus, surplus 6 aluminum is blown from all these portions of the valve by a single annular jet or stream of air. In like manner, air which is forced upwardly through the central air inlet tube 48 is forcibly projected against the end face of the valve head and removes excess molten aluminum from the surface thereof. The coating metal removed from the valves falls through the central chamber 36 and out of the bottom of the device.

'Ihe orifice 34 is preferably arranged to direct the compressed air ygenerally normal to the valve seating face. Hence, the orice passage is shown as being at a 45 angle relative to the valve axis. For optimum results, it has been found desirable to locate the valve so that the air impinges against its seating 'face approximately 1/32 inch from the edge of this face nearest the valve stern.

Of course, it is desirable to provide a more or less permanent means for mounting the poppet valve in proper stationary position within the central chamber 36. can be done by holding the valve in a suitable clamp 54 attached to the device or otherwise properly located relative to it. It is preferable to design the clamping means to engage the ring grooves normally provided near the ends of poppet valve stems since, in this manner, a series of valves all may be maintained in the same relative position within the chamber. In accordance with the invention, therefore, the valve is not subject to whipping or other movement while it and the coating metal are still red hot during the air blast, but is held fast in a Vertical position.

Only the seating face of the poppet valve shown in the drawing has been coated, as indicated by the stippled area of FIGURE l. When only this portion of the poppet valve is provided with the coating, it is not necessary to use the central air inlet tube 48 since excess coating material need not be removed from the end face of the valve head. Moreover, even if this end face is coated, the air passing through the .annular orifice 34 provides an air foil eect which removes much of the excess coating material from the end face of the valve head. Of course, the distribution or thickness of the coating on the valve end face is not critical from the standpoint of iitting with mating parts since this portion of the valve does not contact any part of the engine in which it is used. The only problem, therefore, is that of iiaking off or spalling of the coa-ting on the head end face of the valve if this coating is excessively thick. Because of the aforementioned air foil effect, however, the central air inlet tube 48 appears to be necessary only when the head end faces of large size poppet valves are being coated or when the valve heads have concave end surfaces, as is frequently the case with intake valves.

It will be noted that the inner sleeve 14 has a reduced diameter at its lower end, as shown at 56, to provide for lateral enlargement of the air passage or chamber 16 at its lower end and for lan air inlet opening 40 of suitable size. The formed annular manifold 58 also helps promote the equalization of air pressure within the passage 16 before the air passes through the orifice and impinges on the coated valve seating face. Of course, this eect likewise may be produced by means of a manifold base plate attachment which is not integral with either of the sleeves. Air pressure equalization is further assured by the location of the `air inlet opening 4i) at an appreciable distance axially from the annular outlet or oriiice 34 and by the angular arrangement of this oriiice which necessitates substantial reversal of the direction of air iiow before the air contacts the valve.

In this manner the air is evenly distributed throughout the periphery of the oxice while passing therethrough and, by positively removing the excess aluminum and providing a smoothing or level effect, results in -a smooth,

even, thin aluminum coating on the valve seating face..

Thus, the above-described device for removing excess molten aluminum from poppet valvesprovides auniform air blast on all surfaces of the valve head Without having to subject the valve to rotational Vor other undesirable movement. Y

. Adjustability of the size of the annular orifice 34 permits regulation ofthe volume of air passing through the orifice per unit 'time and the velocity of this air stream. For optimum results it is desirable that the air pressure inthe line supplying air to the orifice be maintained between approximately 75 and 110 pounds per square inch, a pressure of 90 pounds per square inch, for example, providing excellent results. An air blast of 1/2 to 4 seconds duration is preferred, and it never need be longer than ten seconds. After this period of time the aluminum coa-ting on the seating face ofthe poppet valve will have solidified. Other gases or vapors could he used to provide the high-velocity jet for removing the surplus coating metal, of course, but compressed air is Y least expensive and highly effective.

It will be appreciated, of course, that when the same fixture is used for processing different size valves the air pressure and orifice size should be adjusted accordingly. Ina'smuch as the :criticality of the aluminum coating is restricted primarily -to the valve seating face, a poppet valve having a relatively large diameter head necessarily should be subjected `to an air stream having a somewhat lower air pressure than a valve having a lesser diameter head where the same fixture 4is used to remove excess coating metal from the seating yfaces of valves of both sizes. Best results are obtained, however, when the diameter of `the inner sleeve is approximately 1A inch larger than the diameter of the valve head.

yAs a result ofthe above-described treatment, a uniform aluminum coating is provided on the appropriate surfaces of the poppet valve, and the thickness of this coating may lbe carefully regulated. In turn, the thickness of the intermediate iron-aluminum alloy layer may be controlled and, as hereinbefore described, it is this alloy layer which is primarily determinative of the life of the valve. Moreover, not only is the resultant aluminum overlay uniformly thin and a thin, even intermediate aluminum-iron alloy layer produced, but lthe dimensions of the seating faces of the valves so processed will not be disadvantageously affected during removal of the surplus molten coating material.

The thin coating thus provided on a poppet valve head eliminates the possibility of run-down of the coating metal due to melting while the valve is in operation in an engine. An interference fit at the valve seating area might otherwise result. Moreover, the non-uniform coating which is normally produced if the above procedure is not followed .y prevents proper installation of a valve in yan engine because the valve seat facing does not conform to the valve seat.

While thisinvention has been described by means of certain specific examples, it will be understood that the scope of the invention is not to be limited thereby except as defined in the following claims.

I claim:

l. A method of providing a thin coating of aluminum onithe head of a poppet valve which comprises immersing the head Vof said valve for a short period of time in a molten uxing salt bath at a temperature between l280 F. and 1400 F., thereafter dipping the head of said valve for not more than ten seconds in a molten coating metal bath selected from the group consisting of aluminum and aluminum base alloys, said bath being maintained at a temperature between approximately 1250 F. and l325 F., removing the valve from said aluminum bath and rinsing the head thereof for a short period of time not in excess of approximately l5 seconds in a iluxing salt to remove some of the surplus molten coating metal from said valve head, thereafter blasting the entire seating face of said valve with air under a pressure of approximately 75 to 110 pounds per square inch for about 1/2 to 4 seconds to `further remove excess coating metal therefrom and to provide a smooth layerA of aluminum-on theseating face of said valve, simultaneously blasting the head end face of said valve for a similar period of time with air under approximately the same pressure, and finally permitting the metal coating to solidify on said valve head.

2.. A method of coating a poppet valve with aluminum whereby a thin alloy layer of the base metal `and the aluminum is formed having a thickness not in excess of about 0.0015 inch which comprises the steps of immers'mg the valve head in a molten fluxing salt bath at a'temperature between 1280 F. and 1400 F., thereafter dipping the valve head in a molten metal bath selected from the group consisting of aluminum and aluminum base alloys maintained at a temperature between approximately 1250" F. and 1325" F., removing the valve head from said aluminum bath and rinsing it-in a molten liuxing salt bath to remove some of the surplus molten coating kmetal from said valve head, thereafter blasting theentire seating face of said valve with air under pressure to remove additional excess molten metal and permitting thev metal coating to solidify on said valve, whereby an alloy layer of the aluminum with the base metal of a thicknessv not in excess 0.0015 inch is formed. n

3. A method of coating a poppet valve with aluminum whereby a thin alloy layer of the base metal and the aluminum is formed havingV a thickness not in excess of about 0.0015 inch which comprises the steps of irnmersing the valve head in a molten fluxing salt bath at a temperature between 1280" F. and 1400 F., thereafter dipping the valve head in a molten metal bath selected from the group consisting of aluminum and aluminum base alloys maintained at a temperature between approximately l250 F. and 1325 F., removing the valve head from said aluminum bath and rinsing Iit in a molten fluxing salt bath While rotating it to remove some of the surplus molten coating metal from said Valve head, thereafter projecting a stream of air under pressure against the seating face of said valve in a direction generally perpendicular to said seating face and permitting the metal coating to solidify on said valve whereby an alloy layer of the aluminum with the base metal of a thickness not in excess of 0.0015 inch is formed.

4. A method of coating a poppet valve with aluminum whereby a thin alloy Ylayer of the base metal and the aluminum is'formed having a thickness not Vin excess of about 0.0015 inch which comprises the steps of immersing the valve head in a molten fiuxing salt bath, thereafter dipping the valve head ina molten metal bath selected from the group consisting of aluminum and aluminum base alloys maintained at a temperature between approximately 1250 F. and 1325." F., removing the valve head from said aluminum bath and rinsing it in a molten fluxing salt bath to remove some of the surplus molten coating metal from said valve head, thereafter blasting the seating face of said valve with air under-pressure for a time suiiicient to further remove excess molten metal and to cause the aluminum to form an alloy layer with the base metal of a thickness not in excess of 0.0015 inch on cooling.

5. A method of coating a poppet valve with aluminum whereby a thin alloy layer of the base metal and the aluminum is formed having a thickness not in excess of about 0.0015 inch which comprises the stepsof'immersing the valve head in a molten uxing salt bath, thereafter dipping the valve head in a molten metal bath selected from the group consisting of aluminum and aluminum base alloys maintained at a temperature between approximately 0 F and 1325 F., removing the valve head from said aluminum bat-h and rinsing it in a molten uxing salt bath to remove some of the surplus molten coating metal from said valve head, thereafter directing an annular jet of compressed air against the seating face of said head to further remove excess molten metal therefrom and permitting the metalY coating to solidify on saidV valve,

10 whereby an alloy layer of the aluminum with the base 1,976,596 Austin Oct. 9, 1934 metal of a thickness not in excess of 0.0015 inch is 2,273,250 Charlton Feb. 17, 1942 formed. 2,569,097 Grange et al Sept. 25, 1951 2,930,106 Wrotnowski Mar. 29, 1960 UNITED STATES PATENTS 5 References Cited in the le of this patent 1,907,034 Austin May 2, 1933 

1. A METHOD OF PROVIDING A THIN COATING OF ALUMINUM ON THE HEAD OF A POPPET VALVE WHICH COMPRISES IMMERSING THE HEAD OF SAID VALVE FOR A SHORT PERIOD OF TIME A MOLTEN FLUXING SALT BATH AT A TEMPERAURE BETWEEN 1280*F. AND 1400*F., THEREAFTER DIPPING THE HEAD OF SAID VALVE FOR NOT MORE THAN TEN SECONDS IN A MOLTEN COATING METAL BATH SELECTED FROM THE GROUP CONSISTING OF ALUMINUM AND ALUMINUM BASE ALLOYS, SAID BATH BEING MAINTAINED AT A TEMPERATURE BETWEEN APPROXIMATELY 1250*F. AND 1325* F., REMOVING THE VALVE FROM SAID ALUMINUM BATH AND RINSING THE HEAD THEREOF FOR A SHORT PERIOD OF TIME NOT IN EXCESS OF APPROXIMATELY 15 SECONDS IN A FLUXING SALT TO REMOVE SOME OF THE SURPLUS MOLTEN COATING METAL FROM SAID VALVE HEAD, THEREAFTER BLASTING THE ENTIRE SEATING FACE OF SAID VALVE WITH AIR UNDER A PRESSURE OF APPROXIMATELY 75 TO 113 POUNDS PER SQUARE INCH FOR ABOUT 1/2 TO 4 SECONDS TO FURTHER REMOVE EXCESS COATING METAL THEREFROM AND TO PROVIDE A SMOOTH LAYER OF ALUMINUM ON THE SEATING FACE OF SAID VALVE, SIMULTANEOULY BLASTING THE HEAD END FACE OF SAID VALVE FOR A SIMILAR PERIOD OF TIME WITH AIR UNDER APPROXIMATELY THE SAME PRESSURE AND FINALLY PERMITTING THE METAL COATING TO SOLIDIFY ON SAID VALVE HEAD. 